1. Field of the Invention
This invention relates to ALMT1-1 gene, which is a novel gene of aluminum-activated malate transporter of a plant, and a protein encoded by the gene.
2. Description of the Related Art
Food crisis caused by increase in population and alteration in environment is expected to occur in the near future. Therefore, in order to cope with the problem, there is a great demand on development of an agricultural technique that enables efficient production of crops. In the world, there are various kinds of unfertile soils that inhibit plant growth and it is a serious problem on crop production. Especially, acid soils comprise 40% of arable land and the soils spread all over the world including Japan, China, Southeast Asia, Australia, North America and South America. Therefore, for the purpose to increase food production, it is important to improve crop productivity in the acid soils.
For the purpose to achieve increased crop production in acid soils, breed improvement has been performed mainly on chief grains such as wheat, rice, barley and maize. Selection of aluminum-tolerant cultivars and the improvement of breeds by crosses to the other cultivars has been carried out. However, such procedure consumes enormous time and labor. On the other hand, one example on production of aluminum-tolerant crops by the technique of gene recombination has been reported. For example, citrate synthase gene derived from soil inhabiting bacteria was introduced into crops such as tobacco. The transgenic plant excessively synthesizes and exudates citrate which can form a complex with aluminum, then exhibits aluminum tolerance. However, in this technique, citrate efflux from the plant occurs constitutively, regardless of presence or absence of aluminum ion. Therefore, it may cause decreased productivity in the crop. Moreover, because the transgenic crop is introduced with a gene derived from soil inhabiting bacteria, problem in safety of such crop as a food or feedstuff still remains. In addition, reproducibility of this procedure has not been confirmed yet.
In acid soils, aluminum (Al) ion is the main factor inhibiting plant growth. Investigation on Al-tolerant gene has been carried out and existence of the Al-tolerant gene has been predicted. It is assumed that expression of the gene enables Al-activated malate efflux from wheat. A wheat expressing this gene is assumed to exhibit Al-tolerance, since malate forms a complex with Al ion to inactivate the Al ion.